Caffeine probably doesn't jump to mind as the most fearsome substance your kids can ingest.

That said, a few headlines in recent weeks are a good reminder that caffeine comes in many forms and that there's still a lot that we don't know about its impacts. A recent study in Pediatrics found different blood pressure and heart rate responses in boys and girls after puberty, and that girls' responses can vary during their menstrual cycle.

And last week, Oregon Attorney General Ellen Rosenblum filed a lawsuit against the makers of 5-Hour Energy, alleging they are making false, deceptive and unsubstantiated claims about its concentrated caffeine drink. Among the lawsuit's claims: that the product's marketing implies it is safe for those 12 and older.

Over email, we asked Dr. Zane Horowitz, medical director of the Oregon Poison Center at Oregon Health & Science University, a few questions about the impact of caffeine on kids and teens.

1. Should parents be concerned about caffeine consumption by kids and teens? What are the health effects?

Parents should be concerned (or involved) in everything their children do. Just because something is generally available, over the counter, or legal does not mean it's safe for everyone. The child's underlying health problems especially history or heart, lung or seizure disorders need to be taken into consideration for children (and also for adults) who may consume more than an occasional caffeine-containing beverage.

Excessive caffeine causes stimulation, racing heart rates, elevated blood pressure, risk of seizures and changes in metabolism. If the child has a health problem where any of these effects are not desirable, then caffeine should be avoided.

2. How much is too much?

In an otherwise healthy adult or teenager, a drink or two of coffee, or an energy drink per day is safe. Drinking more than a single serving at one sitting increases risk and more than five per day or at once is outright risky.

3. What are the biggest sources of caffeine for kids and teens?

Both coffee and energy drinks have caffeine, and the label for commercial products should list the mg amount. A large coffee may contain up to 200 mg of caffeine. Most contain less. Caffeine powder as sold on the Internet may not list how much is in it and should be avoided altogether. If you can't verify what is in something, don't put it in your mouth is always a good rule.

4. Any thoughts on whether these energy drinks are ever safe for kids/teens?

One energy drink a day for a teenager with no heart problems or seizure history is probably safe. There is no reason any grade school child needs an energy drink to get through a typical day. Using any of these products to stay awake to study or to drive is a bad idea.

5. What about soft drinks?

"The worst thing in soft drinks is the sugar," he said in an email. "Young children should probably avoid caffeine." If they absolutely have to have it? Limit them to no more than 14 to 16 ounces of soda a day.